I. Field of the Invention
The invention relates to an apparatus for protection of electronic circuits in general, and to an apparatus such as this having a decentralized power supply, in particular.
II. Description of the Related Art
In the course of the continuously increasing miniaturization and integration of electronic circuits, different functional units are typically accommodated on a board. In this case, different functional units are frequently operated from different power supplies on the board, or in a decentralized manner. This is particularly necessary when functional units or components with different operating voltages, for example 2.5, 3.3 or 5 volts are used on the same board.
Despite having a decentralized power supply, the functional unit [sic] are at least functionally networked. This leads to the problem that, if the supply to one functional unit fails, in particular in the event of a voltage failure, for example due to a short to earth, circuits in other functional units which are connected to the components of the functional unit of the failed supply network can likewise become involved.
If, for example, an output driver which is located within a functioning functional unit drives an input driver which is located in the functional unit of a failed supply network, then the output driver may possibly itself be short-circuited via the input diode of the input driver. As a result, the output driver may become involved because of the power loss caused by the short circuit current, and in the worst case it may even be completely destroyed.
This can in turn lead to damage to circuits in further functional units, as a chain reaction.
One object of the present invention is thus to provide an apparatus which protects electronic assemblies, in particular in the case of decentralized power supplies, against overloading.
A further object of the invention is to prevent, or at least to reduce, damage to further components in a functional unit or in another functional unit when damage occurs to components in this functional unit.
The object of the invention is achieved in a surprisingly simple manner just by the subject matter of Claim 1.
The apparatus according to the invention protects, in particular, electronic circuits and comprises a first and a second power supply as well as a first and second load, which are associated with the first and the second power supply, respectively. A monitoring circuit monitors the function of the first and/or the second load and/or the first and/or the second power supply. If, for example, a malfunction occurs, in particular a voltage failure, the first and/or the second power supply can be controlled and/or switched off by means of the monitoring circuit.
The power supply to all the loads can thus advantageously be switched off when a malfunction, for example a short circuit, occurs in one of the loads. Control or disconnection may, however, also be carried out in the event of failure of one of the power supplies. This advantageously avoids, or at least reduces, damage to components which are still intact, including damage to components in loads other than that which is faulty.
The output voltage from the first and/or from the second power supply is preferably monitored in order to detect any voltage drop below a first or, respectively, second predefined voltage threshold.
The control or disconnection of the power supplies is preferably carried out on their primary side.
In one preferred development, the monitoring circuit is supplied in a redundant manner from the first and the second power supply. This has the advantage that the monitoring circuit is still supplied with power for as long as at least one of the power supplies is functional.
The monitoring circuit preferably comprises a first and a second monitoring device, which are respectively associated with the first and the second power supply, and monitor them respectively. The output voltage from each individual power supply is thus advantageously monitored.
The disconnection preferably takes place within a short time after detection of the malfunction by at least one of the monitoring devices, preferably more quickly than a time which is matched to the application, for example more quickly than 300 ms, particularly preferably more quickly than 30 ms, and particularly preferably more quickly than 3 ms.
The first and the second monitoring device preferably transmit a respective first and a second control signal, which assumes a fault state in the event of the output voltage from the first or second power supply, respectively, falling below the first or second predefined voltage threshold respectively. The first and the second voltage threshold can be preselected independently of one another by means of the first and second monitoring device, respectively. The first and the second control signal of the first and of the second monitoring device, respectively, are subjected to a logic-OR process, so that the logic device emits at its output a third control signal, which defines a fault state while at least one of the two monitoring devices detects a voltage drop, for example a corresponding voltage threshold being undershot.
The first and the second power supply are preferably supplied from the same voltage source, preferably a DC voltage source, for example a battery, and/or by means of a supply rack.
A first switch of the voltage source is preferably associated with the first and the second power supply, so that the first and the second power supply can be switched on and off, preferably simultaneously, by the first switch.
One preferred development comprises a second switch, which receives the third control signal from the logic device and, when this control signal assumes the fault state, disconnects all the power supplies, that is to say carries out a fault disconnection.
The second switch preferably comprises conductive decoupling, for example an optocoupler, comprising a light-emitting transmitting diode and a photosensitive thyristor, so that an input and output of the second switch are electrically or conductively decoupled.
A first resistor is preferably connected in series with the thyristor, to ensure that a sufficient holding current holds the thyristor active, even when the light-emitting transmitting diode is likewise switched off as a result of the fault disconnection.
One preferred development comprises a third monitoring device which is supplied in a redundant manner from the first and the second power supply and transmits a fourth control signal or veto signal to the logic device. When the apparatus is started up or switched on, the third monitoring device ensures that the logic device does not produce a fault signal even though the output voltages from the power supplies have not yet reached the nominal value or operating value. The veto signal from the third monitoring device assumes a veto state for at least as long as the nominal voltages of the first and of the second power supply have not been reached, or have not yet been reached. The veto signal is preferably switched from the veto state to a non-veto state with the delay, thus ensuring that, when the apparatus is being started, the veto state lasts for longer than the fault state of the first or of the second control signal from the first and the second monitoring devices, respectively. This prevents undesirable fault disconnection, and an oscillation state.
One preferred development of the invention comprises further power supplies, loads and monitoring devices, with one load in each case being associated with one power supply and one monitoring device in each case being associated with one load. In particular, 3, 4, 5, 6 or more of these functional units or supply units are provided in each case.
In this case, where there are a number, preferably the same number, of power supplies, loads and monitoring devices, the monitoring devices are supplied in a redundant manner from essentially all the power supplies, and the control signals from essentially all the monitoring devices are subjected to a logic OR operation. This advantageously results in disconnection of all the power supplies if the output voltage of at least one of the power supplies falls below the predetermined threshold value and the protection mechanism according to the invention is functional, provided that at least one of the power supplies is still operating.
The invention will be explained in more detail in the following text using preferred embodiments and with reference to the drawings, with identical or similar components being provided with the same reference symbols.